- Ayano Tateyama: Ayano is his daughter, who discovered the goals and plans of the snake within him, and committed suicide in an attempt to stop it.
- Ayaka Tateyama: Ayaka is his deceased wife, whom he met at university and cared for deeply. After her death, Kenjirou became even more worryingly absorbed in his research. He seemingly made a deal with the Snake of Clearing Eyes, where it promised that Ayaka could be brought back to life if Kenjirou assisted with its plans. At the end of the anime, he is seen reunited with her in the Heat Haze.
- Momo Kisaragi: Momo is his student; Kenjirou helps her, because she is unable to go to school due to her being an idol.
- Takane Enomoto: Kenjirou's former student. It is possible that it was he who injected her with the poison that took her life. However it is unknown if he is aware of her existence as Ene. Takane's body would stay in Kenjirou's laboratory for two years.
- Haruka Kokonose: Another one of Kenjirou's former students. Konoha was originally a video game character Haruka made, which Kenjirou brought into the real world by killing Haruka and trapping him in the Heat Haze.
- Konoha: Konoha currently resides at his house as a foster child. At one point, he has stated that Konoha is the "key" to re-opening the next Heat Haze.
- Hiyori Asahina: Kenjirou's sister-in-law. He offered to get her an autograph from Momo, resulting in her and Hibiya taking up lodgings at his house.
- Shuuya Kano, Kousuke Seto, Tsubomi Kido: Along with Seto and Kido, Kano was adopted by the Tateyama family. Kenjirou was a very good father to his four children, making no difference between the four. Kenjirou's snake uses his body and to give orders Kano to do as it wishes, with the threat that it will kill the rest of his family if he does not comply.
- Snake of Clearing Eyes: Kenjirou was the Snake of Clearing Eyes' "Master." Through his body, the Snake worked to attempt to combine all of the snakes in order to grant Kenjirou's wish to see his wife again. It deliberately extended the time in which it took to grant Kenjirou's wish through the many resetting of routes, all in an effort to exist longer as it can only remain sentient, or conscious, when it is granting a wish. It is unknown if Kenjirou knew of the loop the Snake was causing, but it had openly stated that Kenjirou did not want his family to die, even though his wish required that it be so. However, if Kenjirou had in fact objected to these deaths remains to be seen.